Recorder.



C. W. BERRY.

RECORDER.

APPLICATION FILED JUNE 14, 1910.

Patented May 9,1916.

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RECORDER.

APPLICATION FILED'JUNE 4, 1910.

Patented May 9,1916.

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Patented May 9,1916.

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RECORDER.

APPLICATION FILED JUNE 14, 1910.

Patented May 9,1916.

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RECORDER.

APPLICATION FILED JUNE 14. i910.

Patented May 9, 1916.

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RECORDER.

APPLICATION FILED JUNE 14, 1910. 1,182,628. Patented May 9,1916.

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RECORDER.

APPLICATION FILED JUNE I4, 1910- 1,182,628. Patented May 9,1916.

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RECORDER. APPLICATION FILED JUNE 14, 1910.

1,182,628. Patented May 9,1916.

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with/eases lvv/vmtor fm a Charles wBe/rr that the proportional CHARLES W. BERRY, OF WEST SOMERVILLE, MASSACHUSETTS.

RECORDER.

Application filed June 14, 1910. Serial No. 566,882.

State of Massachusetts, have invented an Improvement in Recorders, of which the following description, in connection with the accompanying drawings, is a specification, like letters on the drawings representing like parts.

This invention relates to apparatus for producing displacements proportionate to the variations in the properties of a saturated vapor which are derived from or proportional to variations in other properties of the vapor.

The utilization of any two properties of a perfect gas to record variations in other properties of the gas is capable of fairly simple mechanical solution since the substance is homogeneous and follows therefore the same physical laws throughout its entire mass. In Patent 1,093,24l4, granted April 14, 1914i, I have shown an apparatus for recording various properties of a perfect gas. The equivalent problem in the case of saturated vapor presents a further difliculty due to thesimultaneous presence of two phases or physical states of the substance i. c. the liquid and vapor states, so distribution by weight between these two phases must be automatic'ally determined or provided for by the mechanism. Thus, for example, the varying quality of the steam in an engine cylinder, influenced as it is by heat interchanges with the cylinder walls, must be measured and utilized by the recording mechanism.

The properties of temperature and pressure are dependent solely upon the state of molecular activity of the vapor and are wholly independent of the distribution of mass between the liquid and dry vapor phases. The properties of specific volume, specific entropy, specific internal energy and specific total heat however are dependent not only upon the state of molecular activity but also upon the distribution of mass between the liquid and vapor phases, so that the determination of the last-named properties therefore necessitates a preliminary determination of the quality of the vapor. When this is known, any or all of the spe cific properties, volume, entropy, internal energy or total heat can be readily obtained Specification of Letters Patent.

Patented May 9, 1916.

provided themomentary pressure or temperature is also known.

I have found that by utilizing the well known laws of saturated vapors, and by pro vidlng mechanism which takes into account the quality of the vapor, it is possible to delineate variations in any one of the abovenamed properties of a vapor referred to variations in a second property of the vapor by means of displacements proportional to variations in two properties of the vapor, one of which at least is different from the delineated properties. For example, by utilizing displacements proportional to the pressure and volume variations in vapor, displacements proportional to variations in entropy may be obtained. This may be accomplished either by a direct recording apparatus or by a projecting or tracing apparatus, which latter is adapted to reproduce from one curve representing certain physical changes another curve representing other physical changes. Through the use of my invention an indicator card may be directly secured from the steam engine or other motor or compressor utilizing a saturated vapor, showing the temperature-pressure, temperature-volume, pressure-entropy, volume entropy or temperature-entropy variations of the vapor during the engine cycle. This affords opportunity for studying the direction and magnitude of the heat interchanges between the vapor and the walls of the engine, motor or compressor cylinder and for securing other information which heretofore has been obtainable only through indirect calculation from the cards of the ordinary pressure-volume indicator.

With the increasing refinement which has taken place in engine design and the use of more highly perfected materials and workmanship, investigation of the cylinder heat losses and heat changes has become of great importance. To show the nature and magni tude of the heat interchanges, temperatureentropy diagrams have heretofore been plotted from the pressure-volume diagram by calculating the temperature and entropy of a sufficiently large number of points to produce a reasonably accurate curve or have been constructed by complicated graphical methods. This, however, requires the expenditure of so much labor and time that the production of such a curve constitutes a mathematical feat rather than a practical llil aid to engine study and design. Notwithstanding the great value to the designer or engineer of the results obtainable from a temperature-entropy diagram, the labor is so excessive and the principles involved so obscure except to those trained in thermodynamics that the specialist uses such heat diagrams but seldom and the ordinary engineer scarcely at all.

Through my invention temperature-em tropy diagrams, and diagrams showing either temperature or entropy variations plotted against either pressure or volume variations, can be produced without calculation. and by methods and apparatus as readily available and applicable as those employed in securing the ordinary pressure-volume indicator card. The magnitude and character of the heat changes can thereby be easily ascertained and a betterment of the running conditions of the engine secured by minimizing its heat losses.

The mechanical construction of recording devices having the purposes stated may be widely varied to secure the desired relative movements between the recorder and the re cording surface, and my invention is susceptible of embodiment in a great variety of forms. I have hereinafter described for illustrative purposes several forms of the invention from which, in connection with the accompanying drawings, my invention will be best understood, while its scope will be more particularly pointed out in the appended claims.

In the drawings: Figure 1 is a diagrammatic representation of a projector for drawing the temperature-volume curve of a satu rated vapor from the pressure-volume curve, or vice versa. Fig. 2 is an indicator for directly recording the temperature-volume variations of a saturated vapor; Fig. 3 is a diagram showing a means for representing the pressure variations of a vapor while utilizing displacements proportional to temperature variations; Fig. 4 shows the principle of the indicating device represented in Fig. 3 embodied in a recording indicator for recording the pressure-volume variations of a vapor from temperatureand volume-caused displacements; Fig. 5 shows one form of recording indicator for recording variations in the specificvolume of a body of saturated vapor with relation to pressure variations therein; Fig. 6 is a diagram showing the relations between various curves representing variations in several characteristic proper ties of a saturated vapor. Fig. 7 shows a form of projector for drawing the pressureentropy or pressure-volume or volume-entropy curves of a saturated vapor, any one or more from another; Fig. 8 shows one form of recording indicator for recording the volume-entropy or pressure-entropy variations of a saturated vapor; Fig. 9 shows a projector for converting the delineation of the temperature-entropy variations of a saturated vapor into volume-entrqay variations or vice versa; Fig. 10 shows the manner in which variations of the properties of a vapor may be represented by three related curves in the same plane, but shown relatively to different sets of axes representing different properties of the vapor; Fig. 11 shows how the same variation in the properties of the vapor may be represented by a curve in three dimensional space; Fig. 12 shows the essential elements of a recording indicator wherein the recording movement is effected with relation to three mutually perpendicular coordinate planes, but no attempt is made to obtain practicability of operation; Fig. 13 is one form of indicator showing simplified form necessary to obtain reduced inertia of pencil motion; Fig. ll shows an optical indicator of a form some what similar to that shown in Fig. 13, but herein the movement of the pressure responsive member is modified to cause it to move in accordance with variations in the temperature, and where its inertia is still further reduced; and Fig. 15 shows a simplified form of indicator for recording simultaneous variations in entropy, total heat, and internal energy.

As is well known in the case of saturated vapors, there is a definite vapor pressure corresponding to each temperature. The values of the pressure corresponding to different temperatures vary with different vapors, but for all. common substances these variations have been determined and are readily found in any treatise on saturated vapors. If such a temperature-pressure relation be plotted to scale, with reference to rectangular coordinate OT and OP, it Will be represented by a smooth curve which may have the general contour shown at 1 in Fig. 1. This curve. termed herein the PT curve, is dependent for its precise shape upon the particular nature of the vapor. This relation provides a method of project ing a diagram from the PV plane, c. the plane determined by the rectangular coordinates representing pressure and volume. into the TV plane, 2'. e. the plane determined by the temperature and volume coordinates, or vice versa. For example, in Fig. 1 the pressure-volume plane is placed directly above the temperature-volume plane so that the pressure axis OP forms a continuation of the temperature axis OT. At the left of the axis OT there is provided a slot having the contour of the curve 1 and in this slot there is guided a pin 2, the latter secured to the rigidly connected arms 3 and 4 raised at right angles to each other. The arm 3 is adapted to slide freely through a horizontal sleeve which is part of the double sleeve member 5, the latter carrying a tracing point a, which may. be moved freely over the TV- plane to follow the contour of any diagram thereof, such as, for example, the diagram 6 which represents the temperature-volume variations of a saturated vapor such as steam. As the tracing point 0 is displaced vertically to follow variations in temperature, the arm 3 and pin 2 undergo the same vertical displacement and the pin travels along the slot 1 to a point corresponding to the pressure displacement assumed by the tracing point y. This also causes the vertical or temperature displacement of the upright arm a. The latter passes through an upright sleeve 7 mounted on a block 8 sliding in a fixed horizontal slot, so that the arm 4 is always maintained upright. The horizontal movements of the pressure arm a are converted into similar vertical movements of the pressure arm 9 by means of the double sleeve 10 through which both arms 4 and 9 freely slide, the sleeve carrying a pin which works in a fixed slot 11, inclined to the axis OP at an angle of 45 if the scale of pressure remains unchanged. That is to say, as the tracing point :0 moves parallel, with the axis OT to reproduce variations in temperature, the arm 9, which carries the marker y also moves vertically, or parallel to the axis OP to reproduce displacements corresponding to simultaneous variations in pressure. To the marker g there is rigidly connected at right angles to the arm 9 a vertical arm 13 which is slidable through the upright member of the double sleeve 5, so that the marker is guided horizontally or parallel to the axis OV in accordance with horizontal movements of the tracer a: which correspond to the delineated variations in volume. It will thus be seen with the linkage as described and the guiding PT and 45 slots, the displacements of the tracing point as following temperature-volume variations are reproduced in the PV plane by the marker 12 in the form of displacements representing simultaneous pressure-volume variations of the same vapor or vice versa.

Obviously the contour of the PT slot will be different for different vapors, as well as for the different arbitrary scales which may be adopted for the values of temperature, pressure, and volume.

The same principles described in the above projector may be utilized for directly and automatically recording the temperaturevolume curve of a saturated vapor by an instrument resembling the ordinary steam engine indicator. In Fig. 2 I have illustrated such an apparatus, although it will be un derstood that this device, as well as other devices hereinafter referred to, are illustrated in a more or less diagrammatic form in order that the essential parts may not be obscured by details of mechanical construction and the principles of operation may be more clearly presented. The embodiment of this, as well as the other devices referred to in the form of finished and complete mechanical instruments, will be readily understood by those skilled in the art.

Referring to Fig. 2, the marker 3/ is carried upon an arm 20 and is placed in recording relation to a card or other suitable recording surface carried by the cylindrical drum 21 of a construction usual in steam engine indicators. The arm 20 is adapted to slide through the fixed guide 22 parallel with the axis of the drum under the influence of a vertically movable piston 23, which works against the spring 24 within the cylinder 25. The indicator cylinder 25 being connected to the cylinder of a vapor engine or the like, the piston rod 26 has imparted to it a vertical movement responsive to pressure variations of the vapor in the engine cylinder, and this is transformed into a sliding movement of the rod 20 proportionate to temperature variations by means of the slotted arm which has a slot curved to correspond to the PT-curve for the saturated vapor, there being provided the pin 28 adjustably connected to the pis ton rod and working in the slot 27. The drum 21 is turned in one direction by the. usual cord or other flexible member 29 which is connected to the engine cross head through an ordinary form of reducing gear (not shown) the drum being returned to its initial or zero position by an ordinary return spring (not shown) contained within the drum. The displacement of the indicator card. therefore, beneath the marker 1 is proportional to variations in the volume of the vapor, while the momentary displacement of the marker follows the variations intemperature, so that the resulting recorded diagram shows the temperature-volume variations of the vapor according to the chosen scale.

Just as in the case of the projector, where the described relationship between the temperature and pressure of a vapor may be employed for delineating either the temperature volume variations from the pressurevolume variations, or the reverse, so also in the case of a recorder, the pressure-volume variations may be recorded by making use of displacements due to temperature varia tions combined with displacements due to volume variations. This may be useful in special cases where it is difiicult to make a direct measurement of the pressure, and it becomes necessary to utilize temperature variations to produce displacements proportional to pressure variations.

Referring to Fig. 3, I have designated at 40 a mirror which may be attached to the sensitive member of a delicately responsive galvanometer arranged to turn about an axis perpendicular to the plane of the paper in response to current variations of an electric circuit. The circuit in turn being provided with means such as a resistance ribbon or a thermo-electric couple exposed to the varying temperature of the vapor will produce deflections of the mirror 40 as the temperature varies. If OT is a surface having the curvature of a cylinder, a ray of light reflected from the mirror will travel along such surface and assume successive positions along the same with successive increases in the vapor temperature, the equal spaces Ot t t fit, etc. representing equal increments in temperature and equal deflections of the mirror. If instead of the surface OT the surface OP of an irregular form is provided, so that the distances 079 72 79 etc., which are marked off by the ray of light on the surface OP bear the same relation respectively to the distances Ot H etc., as the corresponding changes in pressures do to the corresponding temperature changes, then the pressure variations of the saturated vapor will be correctly indicated by the ray of light upon an equally subdivided scale placed along the surface OP. In Fig. 4 I have indicated more or less diagrammatically andconventionally an apparatus wherein this principle is utilized to record the pressure volume variations of steam or other vapor by means of its volume and tenuierature-caused displacements. Herein the mirror 40 is suspended Within the sensitive galvanometer 41, the latter being in series with a thin resistance ribbon (not shown). By suitably selecting the metal of which the ribbon is composed and designing the circuit so that the ribbon comprises a large proportion of the total resistance of the circuit, the resistance of the ribbon and the current in the circuit may be made to vary with the temperature changes in the ribbon so that when the latter is suitably exposed to the saturated vapor within the engine cylinder the galvanometer mirror will undergo deflections proportional to the tGlIlPQlillllll'G changes in the saturated vapor.

A source of light, such as the arc lamp a2, is provided behind a suitable screen so that only a single light sheet falls upon the mirror, this being reflected in the direction of an irregularly shaped surface or backing l?) having the contourof the line OP in Fig. 3, so that the movement of the light sheet along its face measures pressure changes in the saturated vapor. A sensitive photographic film 44: is then laid upon the backing 4.3, so as to conform to its curvature, such film, however, being shielded from the light by an opaque screen 45 except where the li ht passes through a slot 46, the latter extending lengthwise the screen. The screen is carried by some vertically movable part 47 connected through the flexible connection 48 with the engine cross head, so that the movement of the engine piston will impart a vertical movement to the screen and the slot proportional to volume changes, the sensitive film being then traversed by a pencil of light which acts as the recording medium and is displaced vertically according to volumn changes and horizontally according to pressure changes in the saturated vapor. It will be understood, of course, that the screen, the film and the mirror in the instrument as actually constructed will be suitably protected against the access of extraneous light other than that of the mirror.

A diagram obtained by either of the instruments described in Figs. 2 or 4., as well as the pressure-volume diagram of an ordinary steam engine indicator, gives the record of the changes undergone by whatever weight of saturated vapor may be momentarily present in the engine cylinder or other vapor container used. This vapor will consist of liquid and dry vapor mixed in some unknown and constantly varying porportions. If these temperature-volume and pressure-volume diagrams are to be used as the basis for plotting a specific mass property of the gas, such as volume, entropy, total heat or internal energy, it is desirable to have the indicator take some account of the quality of the vapor and automatically record specific volume or the volume per unit weight of vapor. Where these volumetric displacements are utilized for producing entropy displacen'ients of a vapor, as will more fully appear, it is necessary that such volumetric displacements should be displacements actually proportional to variations in volume of unit weight, and the same is true of an indicator for automatically recording other specific properties of the vapor. For this purpose, I have provided means whereby displacements proportional to the volume of unit weight of vapor may be produced, such unit-wcight-displacement device herein comprising a stroke-modifying mechanism, the function of which is to modify the stroke of the engine piston so as to produce at the indicator in terms of the scale of volume) displacen'ients proportional to the "olume of one pound (or other weight unit) of vapor of the same quality as that of the vapor actually present in the cylinder.

Referring to Fig. 5, I have therein shown an indicator, the function of which will be more fully referred to, to which there is attached a unit-displacen'ient device. This comprises the pivoted unit-weight arm 50 along which there is adapted to slide the block 51, carrying a pin 52 working in a vertical slot on the volume directing arm 53, which latter directs the volume-caused displacements of the marker y. The block 51 is caused to slide along the arm by means of the usual flexible connection 5st to the cross head reducing mechanism, the flexible connection 55 being connected to a suitable spring (not shown) to return the block to its initial position. The arm may be adjusted and clamped in any selected position along the sector 56, its departure from a horizontal position or one in registration with the scale 57 evidently causing an adjustable reduction in the actual stroke or movement of the volume director as related to the actual stroke or movement of the sliding block 51.

To determine the amount of reduction in the stroke of the volume director, preliminary tests should first be made to determine the actual weight of vapor in the cylinder of the engine under test. This vapor comprises the feed portion, which passes through the cylinder at each revolution of the crank shaft, and the remanent portion, which is retained in the clearance space in the cylinder after the closing of the exhaust ports. The feed portion may be calculated by measuring the total vapor used in a given time and dividing this by the number of revolutions in the same time. This gives the vapor per revolution and if the cylinder is doubleacting one-half of this may be assumed to pass through each end of the cylinder.

The remanent or clearance vapor may be computed by observing the percentage of compression and the pressure of compression from the pressure-volume indicator card and thereby calculating the weight of dry vapor at this pressure which would be required to fill the clearance space and the cylinder up to the point of compression. This method of calculating the weight of The value of this reduction factor k is established as soon as the engine dimensions, the scale of the indicator, and the weight of steam are known. Finally the stroke of the marker is equal to If the arm 50 isthen adjusted upon the segment arm 56 so that the travel of the sleeve 51 shall impart to the marker 11 a travel Z the desired reduction in motion is accomplished. It'is evident that the greater part of this adjustment is made with an ordinary reducing motion which gives to the indicator cord 54 a displacement somewhat greater than Z, and that then this greater motion of 51 is reduced to the desired motion of y by adjusting this angular displacement of the arm 50 with reference to the fixed arm 57 upon which the scale of volume in-cubic feet is marked.

vapor in the cylinder obviously assumes substantially constant conditions as regards load, speed and pressure during the tests, but this assumption is attendant upon any measurements of entropy or other specific quality of the saturated vapor whenever any complicated heat balance is made of an engines performance, or whenever ordinary indicator cards are projected into any other plane. Obviously refined computation as well as delicate measurements should only be applied to engines working under good conditions.

Having obtained the total weight of vapor in the cylinder, the required reduction in the travel of the volume director can be calculated as follows: The total horizontal travel of the marker 1 corresponds to the piston displacement divided by the total number of pounds of vapor in the cylinder.

It, therefore there be represented by-Z the total travel of the marker 3 in inches, by s the total travel of the cross head in inches,

s by n the scale of the travel of y in cubic feet per inch, by PD the volume of the piston displacement in cubic ft, by w the weight of the cylinder feed plus the clearance vapor in pounds, there must exist between the various quantities thus defined the simple relations by 7c the ratio of these two distances, or

1.72. ks/rt V w From this it follows that the reduction in stroke cu. ft. per inch of stroke of crosshead per lb. of vapor n cu. ft. per inch of stroke of marker per lb. of vapor The indicator shown in Fig. 5, equipped with a specific-volume recorder as described, provides a means for ascertaining and recording the quality and the changes in the quality of the saturated vapor as, for example, the changing quality in the mixture of the dry steam and water in the steam engine cylinder. This is accomplished by graphically comparing the specific volume, or volume per pound of the dry vapor at any given pressure with the actual volume per pound occupied by the saturated vapor in the engine cylinder.

To record the actual volume per pound the marker y is moved horizontally or parallel to the volume axis by the volume director described, and at the same time is moved vertically through the medium of the arm 58 connected to the piston rod 59 of the indicator by means of the adjustable connector 60. By this means the marker 1/ will trace a diagram like the ordinary pressurevolume diagram, but showing the volume changes in cubic feet per pound. To represent graphically the quality of the vapor, the arm 58 is movable horizontally relatively to the marker y and the director 53, the marker y being carried by a sleeve on the end of the volume director, through which sleeve the rod 58 is slidable. At its end the rod 58 carries a second marker which is caused to draw a curve representing the volume per pound of dry vapor for the various pressures through which it passes. The horizontal movement of the marker 1 is effected by means of a pin 61 carried by the opposite end of the arm 58 and working in a slotted arm, the slot for which latter is shaped to follow the curve representing the pressure-volume variations of a pound of dry vapor.

The connection is provided with a sleeve through which the rod 58 is slidable horizontally permitting its described move ment so that through the pressure-actuated displacement of the connector 60 and the volume displacement of the director 53 the specific volume and pressure changes are represented as well as the momentary quality of the mixture. If desired, the pressure connection or director 60 may carry a third marker g suitably positioned to draw the zero volume line OP, while the volume director 53 may carry a fourth marker 3/ suitably positioned to draw the zero pressure line, thus making readily apparent the relation of the different delineated characteristics of the saturated vapor.

It will be seen that for any given pressure the ratio of the distance of the marker from the zero volume line OP to the distance of the marker 3 from the line OP represents the quality of the mixture and the ratio of the distance of the marker 7 from the marker 1 to the distance of the marker 2 from the zero volume line OP represents the percentage of liquid in the mixture.

Obviously the initial position of the marker must be adjusted with relation to the clearance in the engine cylinder. To facilitate this, I have provided the scale 63 adjustably secured to the indicator parallel with the movement of the volume director. Such a scale has marked thereon the gradu ations representing the volume in cubic feet corresponding to the scale of the dry vapor slot 62. At the left of the zero mark on the scale there are provided graduations to the same scale, but measured to the left. That graduation expressing the volume of ea h clearance in the same sense that Z represents the piston displacement is brought beneath the pointer 64 which is in line with the zero volume line OP and the scale fixed in that position. The cord 54 is then so adjusted that at the beginning of the piston stroke any suitably positioned reference mark, such as the V-shaped opening 65 on the volume director, will stand at the zero mark. This provides such a condition that the distance from the volume director to the origin is always proportionate to the true volume in the engine cylinder.

For the purpose of recording merely the quality of the mixture, it would be unnecessary to provide the unit weight arm 50, or its equivalent, provided there is employed a differently formed slot 62 for each different cylinder or container for the vapor having a different capacity. It is more convenient, however, to construct this slot for a unit weight of dry vapor and utilize the unit weight arm or its equivalent to record the actual volume per pound by the marker 1 The foregoing method of recording the pressure-volume variations of a vapor is but one instance of a more general method of obtaining one of the specific properties (herein volume) of the vapor, the method of determining the quality of the vapor herein described being utilized also in recording other specific properties of the vapor such as entropy. internal energy, total heat, etc.

Before describing the application of my invention to the recording of entropy or other specific characteristics of a vapor,brief reference will first be made to the graphically represented characteristics of saturated vapors relatively to the pressure-volume characteristics of such vapors.

As the. temperature of a dry saturated vapor is determined by its pressure, it fol.- lows that the volume both of the liquid and the vapor, as Well as the entropy of the liquid and its vapor. are functions of the pres sure alone. The value of these functions of the pressure are expressed in the case of different substances by empirical formuhc based upon experimental data.

In Fig. 6 the curve may be taken as an illustrative example of the PT-curve for a saturated vapor, or that expressing pressure-temperature relations. and since the pressure is independent of the quality, this expression is independent of the amount of moisture present. In the PV-To-(temperature entropy) and Va (volume entropy) planes, however. since the volume and entropy are mass functions. there is both a liquid and a dry vapor curve. the liquid curve in the T p-])lane being shown at 71 and the dry vapor curve at 72. Similarly in the Vo-plane the liquid curve is shown at 73 and the dry vapor curve at 74-. and. in the PV- plane. the liquid curve at 75 and the dry vapor curve at 76.

If any constant pressure vaporization. such as ab, in the PV-plane is considered. this will be represented by the point (17) in the PT-plane, by the line a 7) in the Teplane, and by the line a b in the Vo-plane.

l i i i In other words, the line a b and the line a 6 represent conditions of constant vapor pressure in expanding from the liquid to the dry vapor state, the entropy and volume of the mixture at any given moment in such expansion determined by the quality of the mixture. If the pressure be changed so that the constant pressure line is shifted to some new position in the PV-plane, such as 0d, the corresponding constant pressure lines in the T pand Vcpplanes will correspond ingly shift to the positions indicated at 0 d and and 0 (Z respectively. In Fig. 7 I have utilized these principles in the construction of a projecting apparatus whereby by means of the .pressure-volume diagram there may be delineated the volume-entropy diagram (or the pressure-entropy diagram), such projector utilizing a path defining member adapted to be positioned according to the momentary pressure of the vapor and define in any position a constant pressure path along which the required point must be. This member corresponds to the constant pressure line a b of the diagram shown in Fig. 6 and comprises a floating link or rod of variable length and position adapted to occupy in the volume-entropy plane the position corresponding to the pressure of the vapor. Such floating link is herein combined with a sliding block or member thereon carrying a suitable tracing point so controlled by a specific-volume director that it is caused to occupy a position in the volume-entropy plane corresponding to the volume of one pound of saturated vapor of the same quality as exists in the PV-plane at the corresponding point. The marker is thereby caused to draw the volume'entropy variations directly from the pressure-volume diagram.

Referring to the specific mechanism the tracer a: which is caused to follow the outline of the pressure-specific-volume diagram 80, is carried by a sleeve 81 rigidly attached to the horizontal sliding rod 82, the rod being kept normal to the volume axis by means of the sleeve 83 sliding in the vertical fixed slot 84. The rod 82 has sliding movement in a sleeve 85 which carries the marker 3 so that vertical movement of the tracer a; produces a vertical displacement of the marker 3 in the volume-entropy proportional to the specific-volume. In the Ve- -plane at 86 there is formed a fixed guiding slot constituting dry vapor directing means in which slides a pin fastened to a sleeve 87 and at 88 a second slot constituting liquid directing means in which slides a pin 89. These slots are shaped to represent the specific entropycurves for dry vapor and liquid respectively, and serving to position a floating link 90 which constitutes a constant pressure member along which, and between the liquid and dry vapor conditions represented by the slots 86 and 88, the point must lie which represents the condition of the substance. The link 90 has a slot 91 which serves to guide it by means of a pin on the sleeve 87. The position of the g having a pin fixedly secured thereto is also caused to move along the slot 91 in the link, so that it will assume a position along the constant pressure member determined by the volume director 82.

The constant pressure member is variably positioned according to the momentary pressure of the vapor by means of the directors 92 and 93 in the following manner. Slidable vertically through the sleeve 81 is the pressure-directing rod 9%, the horizontal J= movement of which in the PV plane followmg pressure-caused displacements is converted lnto a vertical movement of the d1- rector 95 in the P -plane by means of a block or other guide member 96 rigidly connected to both rods 94. and 95 and slidably guided in the slot 97 arranged at an angle of 15 to both pressure axes. The vertical movement of the rod 95 or that parallel with the pressure axis in the Pap-plane is communicated to the sleeve members 98'and 99, through which the rod 95 is slidable, the sleeves thereby being given horizontal displacements proportional, at any given pres sure, to the entropy of the liquid and the entropy of the vapor, respectively, by means of the directing slots 1,00 and 101 which are shaped respectively in accordance with the pressure-entropy curves for the liquid and the vapor respectively. The marker 1 will therefore record the variations in specificvolume and specific-entropy of the vapor. By providing a marker 1 carried by a sleeve 102 on the end of a rod 103, the

latter so arranged as to be vertically slidable through the sleeve 85, but moved horizontally with the same, the marker y will be caused to record the variations in pressure and specific entropy of the vapor. It is further obvious that either of the markers 12 or y/ may be used as the tracing point and that then y or 7 and will become markers, so that the projector is universal in its action.

It will be seen that the two directing members 82 and. 94. undergo displacements respectively which are responsive to two properties of the vapor, one being a spe- ('ific property, namely specific-volume.. dependent on the mass of the vapor; and the other property, namely, pressures, dependent wholly on the molecular activity of the vapor. The pressuredirector 9 1 with the aid of the liquid and dry vapor guiding means effects a displacement of the constant pressure member 90, so that it always defines the path in the volume-entropy plane of constant molecular vapor activity along which the change from the wholly liquid to the Wholly dry vapor state must take place at any pressure designated by the tracing point in the pressure-volume plane. By means of the volume-director 82 the sliding block of the sleeve 85 carrying the marker is caused to move along the path thus defined by the link in accurate response to changes in the quality of the vapor, so that it correctly designates the point along the constant pressure path which corresponds to the quality of the vapor at the state desig nated by the tracer w. It will be obvious in this, as in the case of all other similar instruments herein described, that the temperature being a function of the pressure, the temperature-volume curve can be employed to plot the volume-entropy curve or the temperature-entropy curve and in the manner just described, it being only necessary to modify the liquid and dry vapor guiding means and 101 respectively, to

make them correctly represent the temperature-entropy changes in the liquid and dry vapor respectively. It will also be evident that the method herein illustrated in plotting properties of a vapor in pairs, that is to say, the entropy referred to the volume, or the entropy referred to the pressure, is not only reversible, but may be extended to include any desired combination of the properties of temperature, pressure, volume, entropy, internal energy, total heat, etc, and is not simply limited to the specific pairs herein indicated. This principle, when used in connection with a unit weight displacement device to modify the actual stroke of the piston, so as to produce in terms of the scale of volume displacements which are proportional to the volume of One pound of vapor of the same quality as that of the vapor actually present in the cylinder, may be employed in connection with a recording indicator to record directly the volumeentropy variations of a saturated vapor or other mass properties of the vapor.

Referring again to Fig. 7, it is evident that the connecting rods for transferring the movements of the pressure director 9 1 from the pressure-volume plane into the pressure-entropy plane could be eliminated, provided the pressure and volume variations occurred along parallel lines,-that is to say. provided the pressure variations could be imparted directly to the constant pressure rod 95. Such a result can be readily obtained in an actual engine indicator where it is merely necessary that the movement of the piston be transmitted directly to the constant pressure arm in the pressure-entropy plane, and that the motion of the cross head be transmitted directly to the constant volume arm in the volume-entropy plane.

In Fig. 8, I have shown a form of direct recorder or indicator for automatically recording entropy-volume variations (or pres- 75 sure-entropy). Herein the marker y is car- 1 ried by a sliding block guided along the con- 1 stant pressure link 104 as it is raised or lowered by the volume-directing arm 105. j The latter receives vertical movement pro- 30 portionate to the variations in specific volume of the vapor in the engine cylinder by j means of the sliding block 106 which is connected to the cross head reducing mechanism, and the movement of which is modified by the unit Weight arm or stroke modifying device 107. The piston rod 108 for the indicator cylinder carries a sleeve 109 in which is horizontally slidable the rod 1.10. The latter at one end carries apin 111 guided by the slot 112 which is shaped according to the pressure-entropy curve for dry vapor. This slot, instead of being located at 112, which corresponds to the position which it occupies in the projecting apparatus Fig. 7, is transferred to the position here shown for the sake of convenience. Its function is obviously the same. At the other end the rod passes through a sleeve 113 carrying a pin guided in the slot 114, 100 the latter shaped according to the pressure- 1 entropy curve for liquid. The sleeve 113 is fastened to an upright rod 115, the horizon tal displacement of which is therefore del pendent on the entropy of the liquid. This rod controls the position of the constant pressure arm 104 relatively to the slot 116 which is the volume-entropy slot for liquid.

The actual position of the constant pressure arm is finally fixed by its relation to the dry 11) vapor guiding slot 117, which is so shaped 1 that it affords the same guidance tothe arm 104, as if it were guided by the dotted line curve 118 which latter corresponds to the volume-entropy line for dry vapor. The relation of the constant pressure arm 101 to the slot 117 is controlled by the upright rod 1 110, the latter connected at one end to the pin 111 and pivoted atthe other to the arm 104. It will be seen that the linkages described move the marker 2 and cause it to record the specific volume and specific entropy variations under the actuation of the pressure director and the specific volume director 105 in precisely the same manner as the marker y of the projector of Fig. 7 is caused to project the specific volume and specific entropy variations into the volumeentropy plane under the control of the vol ume director 82 and pressure director 95.

The indicator shown in Fig. 8 can be made to record the pressure-entropy variations either alone or simultaneously with the record of the volume-entropy record. lhis for example, can be attained as shown in dotted lines by attaching to the part carrying the marker y the downwardly directed arm 120, which has a sliding movement through the double sleeve member 121, the latter carrying the auxiliary marker y. The pressure rod 110 also passes through the double sleeve member 121 at right angles to the arm 120 so that the marker 3 is displaced horizontally by variations in entropy and vertically by variations in pressure. The sleeve 109 is adjustable vertically upon the piston rod 108 so that after the indicator spring is fastened in, it may be moved vertically until the rod 110 comes opposite the point in the Pe-slots 112 and 114 corresponding to atmospheric pressure.

It will be seen that substantially the same principles govern the construction and operation of the projecting recorders and the indicating recorders, the principal difference being that whereas, in the projector the directing member or members are given displacements proportional to variations in the properties of the vapor as delineated in the curve of the diagram, in the automatic indicator, such members are given displacements proportional to variations in the prop erties of the vapor which are caused by the direct action of the vapor itself.

It will be understood that the method herein outlined for recording variations in specific entropy in conjunction with variations in specific volume applies equally well and in a similar manner to variations in other specific mass properties, such as internal energy and total heat, in conjunction with variations in specific volume, and is not to be considered as limited to the precise combination of properties herein described.

Since the temperature, like the pressure, is a property dependent solely upon the state of activity of the molecules and is independent of the quality of the mixture, displacements proportional to the temperature, as previously stated, may be employed the same as displacements proportional to the pressure to obtain displacements proportional to other properties of the vapor.. It will therefore be understood that in the instruments herein described whether projectors or recorders, variations in two characteristic properties of the vapor may be represented in substantially the same way by the use of appropriately shaped guiding members employing displacements based upon temperature variations instead of pressure variations.

In Fig. 9, I have shown by way of illustrating this principle a simple form of projector for converting a temperature-entropy diagram of saturated vapor into a volume entropy diagram or vice versa. Herein I have provided a tracer a; which is movable with reference to the coordinate axes OT and Oe. The tracer is carried by the double sleeve 130 through which latter is slidable the upright rod 131 and the horizontal constant temperature rod 132. The vertical movement of the latter causes the horizontal displacements of the two sleeves 133 and 134: which are guided by the two guiding slots 135 and 136 representing the entropy curves for liquid and dry vapor respectively. This causes the entropy directing rods 137 and138 always to assume a position along the entropy axis corresponding to the entropy of liquid and dry vapor respectively and to appropriately direct the constant temperature rod 139, by means of the jointed connection to the rod 137 at 140 and the sleeve connection to the rod 138 at 141, so that along the constant temperature path defined by such rod, the expansion from the liquid state to the dry vapor state (having reference to the volume and entropy axes shown) always takes place. The sleeve 1&1, which connects the constant temperature rod 139 with the entropy director 138, is guided along the slot 142 which corresponds to the volume-entropy curve of dry vapor, and the directing rod 138 under the mutual guidance of the dry vapor slot 136 and the constant temperature rod 132 causes such sleeve always to assume the requisite position in the slot 142. Similarly the opposite end of the rod 139 is guided within the slot 143, corresponding to the volume-entropy curve for the liquid, so that that end of the constant temperature rod always assumes the requisite position under the guidance of the director 137. To insure alinement, a sleeve 14 1 may be employed to hold the director 138 in an upright position, such sleeve being guided by a block 1 15 working in a slot 146 parallel to the axis 0?. The lower end of the rod 131 carries a sleeve 147 which slides along the constant temperature rod 139 as the tracer a; is moved vertically to correspond to temperature changes. The marker y which is carried by the sleeve 147 is therefore caused to follow the movements of the tracer at, being given a horizontal displacement proportional to the entropy displacements of the tracer 0e and a vertical displacement which, from the preceding discussion, is evidently proportional to the variations in specific volume and follow the temperaturecaused displacements of the tracer It is evident that the simpler form of projector represented in Fig. 9 can always be utilized when only three variables are involved, provided only one of these three rep resents temperature or pressure, while on the 13 other hand more complicated mechanisms, such as already described in Fig. 7, can be designed on similar principles to meet the requirements of any interrelated variable properties of a saturated vapor.

It will be observed that the mechanisms heretofore described for recording variations in the entropy of a vapor by means of displacements caused by variations in other properties of the vapor involved, involves the conversion of a displacement rela tive to two coordinate axes into a displacement relative to other coordinate axes, and also its conversion into a displacement relative to a third pair of coordinate axes. In other words, as described, it involves linkage connections between markers, tracers or other members moving in or with reference to three different coordinate plans. For example, in the projector represented in Fig. 7 tracer w and the markers 1 and y are connected by a rectangularly disposed linkage so that they move correctly in their respective planes, to wit, the pressure-volume, the volume entropy and pressure entropy planes. Substantially the same form of rectangular linkage is provided in the indicator shown in Fig. 8 for geometrically considered the entropy-volume and pressureentropy planes are here superposed one upon the other. These interconnecting linkages whereby the condition of the substance as represented in one plane directly controls the representation of the same property in another plane, while suitable for a projecting apparatus are unavoidably complicated where an indicator is concerned because of the number, weight, friction and inertia of the moving parts which must respond to the high speed reciprocations of both the pressure and volume directors.

A greatly simplified form of indicator can be constructed by basing its design upon a three-dimensional surface, that is to say, a surface positioned in space and located by reference to three coordinate axes representing three properties of the vapor, successive points upon which surface represent the mutual variations of these three properties as the vapor undergoes the change characterized by any curve upon said surface. For illustration, in Fig. 10, the curve 6 may be considered as representing the pressure-volume variations of dry saturated vapor referred to the axes OP and OV, the curve f, the pressure-entropy variations of the same vapor referred to the axes OP and Oq), and the curve 9 the volume-entropy variations referred to the axes OV and Oqa. But these planes may be regarded as arranged in Fig. 11 with the coordinate axes mutually perpendicular so that a threedimensional curve It in space will project upon the PV-plane the curve 6, upon the Pcp-plane, the curve 7, and upon the Vo-plane the curve 9, the

three-dimensional curve It correctly representing the mutual variations of the three properties of pressure, entropy and volume as the vapor undergoes momentary change. here this method of representing variations in the characteristic properties of a saturated vapor is employed, there will be both a three-dimensional liquid curve and a similar dry vapor curve representing the variations in the liquid and dry vapor respectively.

Referring to Fig. 12, I have represented in relation to the coordinate axes OP, OV and Go the three dimensional dry vapor curve is, which has three projections, namely, the curve is, representing the dry vapor curve in the pressure-entropy plane; the curve representing the dry vapor curve in the volume-entropy plane; and the curve .1 representing the dry vapor curve in the pressure-volume plane. The curve Z, represents the liquid line in the pressure-entropy plane, the liquid curve in the PV plane being assumed to be substantially coincident with the pressure axis OP and in the volume-entropy plane with the entropy axis 0a, which, although not true for all vapors, is approximately so in the case of steam. lVith this relation of the three coordinate planes, a curved surface developed by a. guiding rod which remains in a plane always normal to the pressure axis OP, but moves in contact with the curves Z1 and Z will represent in three dimensional space all conditions of the substance between liquid and dry vapor. That is to say, points on such a curved surface will represent conditions ofthe substance which will be conditions of liquid along the curve Z, conditions of dry vapor along the curve is and intermediate conditions between those curves. In the case of a mixture of four parts liquid and six parts vapor, the point will be six-tenths of the distance from the curve Z toward the curve Z2 upon the particular constant-pressure line being then considered. This principle may be utilized in the construction of an indicator by guiding two rods, one a constant-pressure rod so controlled that it shall always occupy a position in space coincident with a constant-pressure line on the above-mentioned curved surface, and the other a volume rod so guided that its displacements from the pressure axis shall always be equal to the volume occupied by the unit weight of the substance, and whose altitude or distance from the volume axis shall always be equal to the pressure. The prolongation of this volume rod will therefore intersect the constant pressure rod at a definite point on the said three-dimensional surface, which point will represent the pressure, specific volume, and specific entropy of the substance. Fig. 12 shows for the purposes of illustration an apparatus whereby this result is obtained. The constant-pressure rod represented at 160 might be guided in slots coincident with the curvesla and Z, but, to facilitate the recording of conditions close to the liquid or dry vapor lines, other slots are employed giving an equivalent movement to the rod, For example, the curved constant pressure surface may be prolongedlto intersect a plane Po parallel to the pressure-entropy plane, thereby deter-v v mining an equivalent curve 161. The intersection of the same surface prolonged with the PV plane determines the curve 162. It is ob- 'vious that if the arm 160 is maintained parallel to the Vo-plane and guided along the curves 161 and 162, it will at all times coincide with the constant pressure surface. For convenience in transmitting the motion of the piston to the constant-pressure rod, there is provided back of the curve 161 the slotted guide 163, in which moves the piece 166i connected to the constant-pressure rod, the slot being in a plane parallel to plane Po and similar incurvature to the curve 161, so that the rod is caused to move along the latter curve. There is also provided the slotted guide 165, which serves to guide: the slide rod 166 pivotally connected also to the constant-pressure rod so that at its pivoted connection thereto the rod 1s obliged to move at all times along the curve 162.

A vertical, or pressure-actuated move ment, is imparted to the constant-pressure rod by means of parallel plates 167 between which the. said rod has free swinging movementparallel to thevolume-entropy plane to follow the guidance of the two guiding members 163 and 165, but by which it is raised or lowered in accordance with variations inpressure under the influence of the pressure cylinder 168 and the piston rod 169. The vertical movement of the plates 167 also causes a like movement of the slide rod 166 which passes through the guiding block 170, the latter being adapted to slide vertically in the vertical guide 171. A volume director 172 is provided, this having sliding movement through the guide block 170, being therefore raised and lowered with the said guide block by the piston rod 169 while at the same time it is moved parallel with the volume axis by the movement of the vertical guide 171. The latter has sliding movement along the fixed slotted frame member 175 and has suitable connection to the cross head through the unit weight arm 17?), so that the displacement of the guide, and, therefore, of the volume director along the volume axis, is proportional to the volume occupied by unit weight of the substance undergoing in vestigation. e

The-volume-director 172 being prolonged meets the pressure rod .160 at 174 being promeetsthe pressure rod 160 and 174 where it intersects the three-dimensional curved surface referred to. The point 174 represents the condition of the substance in question at any given time and its varying projection upon any one of the three coordinate planes will trace the curve for that substance showing the mutual variations between the two coordinate properties. The pressure rod is jointed to the volume director at its union therewith and is so connected to the members 164, 166 and 167 as to be capable of extension or axially movable with relation thereto, with the varying quality of the substance and as required by the movements of. the volume director.

It will be obvious that by suitably apply- .ing marking devices to the instrument shown in Fig. 12 either the pressure-volume, pressure-entropy or volume entropy curves may be drawn or all three curves may be drawn simultaneously. For example, a marker applied to 3 will trace the pressure-volume variations upon a card appropriately posi-. tioned in parallelism with the pressure-vol-. ume plane, while a marker. placed at y will trace the pressure-entropy variations upon a card parallel to the pressure-entropy plane, which card might be attached to a plane carried by the guides 171, and the volume-entropy variations on a card paral lel to the volume-entropy plane, it being understood that such marker or markers will be automatically extensible or other suitable provision made to provide for the variable distance of the point 171 from their respective recording surfaces.

The foregoing construction is referred to in order to illustrate the fundamental actions involved, and as embodying all elements essential to the proper functioning of such an indicator. In Fig. 13 I have shown an indicator working on substantially the same principle so designed, however, as to materially reduce the number, and friction and inertia of the moving parts. Referring to Fig. 13, the constant-pressure rod 180 receives guidance from the slotted guiding members 181 and 182, so that it performs essentially the same movements as does the arm 160 in Fig. 12. The quality-determining mechanism of the indicator in Fig. 12, however, has been replaced by a vertical guiding rod 183 which guides the end of the constant-pressure arm in its vertical movement, said vertical guide. rod being carried by a block 184, guided in the constant-voluine slot 185, the latter carried by the volume director 186. The volume director 186 also carries the recording surface 187 against which presses the marker 3 carried by a sleeve 188, the latter having a free turning movement at the end of the constant-pressure rod 180. The volume director 186 is given a displacement proportional to variations in specific-volume 1n the manner sub stantially as heretofore described, so that the marker or recording medium has the same relative movement to the recording surface that the marker y in Fig. 12 has relatively to the Pqa-plane. The marker therefore will record on the recording surface 187 the pressure variations referred to variations in entropy. In this formof indicator the piston has to operate merely the constant-pressure arm and the controlling linkage therefor, together with the sleeve at the end ofthe arm which carries the tracer y. Itis evident that if a pencil point were attached at 189 to the bottom of the vertical rod 183, such point would trace the volumeentropy diagram upon a suitable recording surface such as 190 held beneath the point. The construction of the other details of the indicatorywill .be evident from the description already given of previous instruments.

In Fig. 14 I have shown a form of optical indicator for indicating temperature-entropy variations. The constant-pressure arm has herein been converted into a constant temperature arm 200 by means of the slotted guide 201 which transforms the pressure responsive displacements of the indicator piston rod 202 into vertical displacements of the directing rod'203 proportional to the momentary temperature.

The apparatus is further lightened by eliminating the pencil or marking point and providing a marker by means of a ray of light which iscaused to pass through the constant temperature arm, the latter being herein in the form of a hollowtube carrying at one end an opaque screen 204 behind which a source of light 205 is placed. As the constant temperature tube rises and falls and at the same time swings along the contour of the requisite three-dimensional surface through the medium of the guiding slots 206 and 207, there is always a ray-of light which will pass through the tube and impinge upon the sensitive plate 208, which herein serves as the recording surface carried by the volume director 209. The parts moved by the indicator piston can be still further reduced as follows: It is evident that the constant pressure or constanttemperature arm, whlchever may be used, describes a certain helical surface in space as the pressure varies. In place of the two guiding slots described in connection 'with the'two preceding instruments it'is therefore possible to utilize a unitaryguide so shaped as to conform to this helical surface and of a suflicient extent to guide the rod within the limits in which record is required. This is feasible, for a projection of'the various constant-pressure lines upon the volume-entropy plane show that at some particular point the prolongations of the various elements of the helical surface are approximately vertically disposed.

In Fig. 15 there is shown at 210 a helical guiding surface adapted to guide the constant tpressure arm 211 in the manner describe so that it will have the same movement as if guided by the two separate slots 181 and 182 in Fig. 13. The marker carried at the end of the rod 211 will, therefore, record the pressure-entropy variations on a recording surface 212, the indicator being otherwise constructed like that shown in 'Fig. 13. As previously stated the internal energy or total heat of saturated vapors have a fixed relationship to the pressure so that these properties can be re corded in the same fashion as the entropy by employing suitably modified guiding members. In fact they may be recorded in the same instrument which records entropy variation. In the instrument shown in Fig. 15, 'I have shown at 213 a helical guiding member adapted to guide-the constant pressure arm 214 so that a marker carried at the end of the arm will record the internal energy variations with reference to the pressure variations and at 215 I have shown a similar guiding-member adapted to guide the arm 216 so that a marker carried by the latter will record the variations in total heat of the substance relatively to the pressure variations in the same manner as the entropy variations are recorded. These devices maybe used separately or simultaneously, it being possible with an indicator of the type described to record simultaneously the pressure entropy, pressure internalenergy and pressure-total-heat diagrams upon the same indicator card.

It will be understood that the indicator shown in Fig. 15, as well as those shown in Figs. 12, 13 and 14 will, in practice, be provided with a. scale similar'to the scale 63 shown in Fig. 5, whereby the volume indicator may be initially adjusted as to its zero point, so that its displacement with reference to the zero of volume shall properly represent the relative values of the clearance, volume and piston displacements.

The indicator shown in Fig. 15 might be preferably constructed to use but a single member being appropriately shaped 

